This invention relates generally to electronic equipment in which a shelf supports a plurality of circuit boards that are slid into position in the shelf, and more specifically relates to the management of the circuit boards.
A rack consisting of a plurality of stacked electronic shelf units minimizes the amount of space needed to hold the electronic circuitry that supports a substantial number of tasks, e.g. a rack of shelf units each with several printed circuit boards can support telecommunication networking services for a substantial number of end-users. In order to provide a high reliability environment and to provide maintenance, control and monitoring of the individual circuit boards in a shelf, a shelf management function is required.
FIG. 1 is a front view of a conventional electronic shelf 10 having a first community of circuit boards 12 including circuit boards B1–B5 and the second community of circuit boards 14 including circuit boards B6–B10. Shelf management controllers 16 and 18 manage the first and second set of shelves, typically operating in an active/standby configuration. Central processing units (CPUs) 20 and 22 are contained by the shelf management controllers 16 and 18, respectively, and provide the intelligence required to process inputs reflecting conditions in the shelf, on the circuit boards, externally generated inputs from craft personnel, and make decisions to control the operation of the respective circuit boards. In high reliability environments in which active backup must be provided in case of failure of a circuit board, an electronic shelf can be organized as two halves in which a first half includes circuit boards that are active and provide current service, and the second half includes circuit boards that are in a hot standby condition where a failed circuit board, e.g. B2, in the active first half is sensed by a management function that causes the similarly positioned circuit board B7 in the standby half to take over the functions of circuit board B2. Alternatively, a shelf can be configured to contain one or more spare circuit boards that can be selected to take over the functions served by any circuit board in the shelf that has failed. The shelf management controllers are typically mounted adjacent the circuit boards served by the management controller as shown in FIG. 1. Alternatively, the shelf management controllers may each comprise a separate circuit board inserted into a slot within the set of circuit boards being served by the controller.
Such management controllers have generally proved effective. However, the use of external management controllers mounted adjacent the served circuit boards such as shown in FIG. 1 take up front panel space within the rack, dissipate power, and are costly. Even if the management controllers consist of circuit boards that are inserted into slots within a shelf, such management controllers occupy space, i.e. slots, that could otherwise be utilized to house additional circuit boards that would provide increased load capability. Thus, there exists a need to provide the functionality of management controllers while maximizing the space available for circuit boards that will in turn maximize the load that can be carried.
FIG. 2 shows a modular electronic shelf 30 in accordance with the Advanced Telecommunications Computing Architecture (AdvancedTCA, also known as PICMG3) standards. It includes a backplane 32 that performs connection and distribution functions between the circuit boards and with external devices and systems. A plurality of front mounted circuit boards represented by circuit board 34 each contain a CPU 36 that provides the primary source of intelligence for implementing functions carried out by the circuit board. A portion of the rear edge of circuit board 34 engages connector 38 that is connected to the backplane 32. Another portion of the rear edge of circuit board 34 engages a connector 40 that facilitates a connection between the circuit board and a rear transition module (RTM) 44. A power source 46 provides and distributes the appropriate voltages and currents required by the various elements in electronic shelf 30. One or more fans 48 take outside air at the bottom front of the shelf and force it upward through the circuit boards where it exits near the top rear of the shelf to provide cooling for the circuit elements contained on the circuit boards. A mezzanine board 50 such as mounted parallel to the circuit board 34 may contain additional circuitry and is connected to circuit board 34 by connector 52. The AdvancedTCA modular shelf is intended to provide a standard for the packaging of telecommunication circuit boards, and specifies physical dimensions and requirements. Shelf management controller 54 is situated below the circuit boards, and connects to system resources through connector 56 and backplane 32, or through cables (not shown).